Residency · Residency · Orthopedic Surgery
Elbow Fractures and Dislocations: The Terrible Triad and Beyond
Overview
The elbow is a trochoginglymoid joint (combining hinge and pivot functions) with three articulations: ulnohumeral, radiocapitellar, and proximal radioulnar. Primary static stabilizers include the ulnohumeral articulation, the anterior band of the MCL (medial collateral ligament), and the lateral ulnar collateral ligament (LUCL). Secondary stabilizers include the radial head, common extensor origin, common flexor origin, and joint capsule. The elbow is the second most commonly dislocated major joint after the shoulder.
Elbow Stability Anatomy
Medial Collateral Ligament (MCL)
The anterior bundle is the primary restraint to valgus stress and the most important component. It originates from the medial epicondyle and inserts on the sublime tubercle of the coronoid. The posterior bundle serves as a restraint to valgus in flexion. The transverse ligament does not cross the joint and makes minimal contribution to stability.
Lateral Collateral Ligament Complex
The LUCL (lateral ulnar collateral ligament) is the primary restraint to posterolateral rotatory instability (PLRI), originating from the lateral epicondyle and inserting on the crista supinatoris of the proximal ulna. The radial collateral ligament (RCL) provides restraint to varus stress. The annular ligament stabilizes the proximal radioulnar joint.
Osseous Stabilizers
The coronoid process is a critical buttress to posterior displacement. The Regan-Morrey classification grades coronoid fractures as Type I (tip), Type II (less than 50%), or Type III (greater than 50%). The O'Driscoll classification subdivides them into tip fractures, anteromedial facet fractures, and basilar fractures. The greater sigmoid notch provides ulnohumeral stability. The radial head is a secondary stabilizer to valgus that becomes the primary restraint when the MCL is deficient.
<image>Anatomy of the elbow ligaments including MCL, LUCL, and annular ligament</image>
Simple Elbow Dislocations
Mechanism and Pathoanatomy
The most common pattern is posterolateral. O'Driscoll's circle of Horii describes sequential disruption from lateral to medial: Stage 1 involves LUCL disruption causing PLRI; Stage 2 adds anterior and posterior capsule disruption producing a perched dislocation; Stage 3a involves posterior bundle MCL disruption causing valgus instability with dislocation; and Stage 3b involves anterior bundle MCL disruption resulting in gross instability.
Management
Closed reduction is performed under sedation. Post-reduction assessment includes stability testing through range of motion to identify the "safe arc" of motion. Early ROM within the stable arc is critical, as prolonged immobilization leads to stiffness. Typically a hinged brace or buddy splint at 90 degrees is used for comfort, with motion starting within 1-2 weeks. Outcomes are generally excellent, though a residual flexion contracture of 10-15 degrees is common.
Radial Head Fractures
Mason Classification (Modified)
| Type | Description | Treatment |
|---|---|---|
| I | Nondisplaced or <2 mm displacement | Sling, early ROM; aspiration for comfort |
| II | Displaced >2 mm, partial head involvement | ORIF (screws and/or mini-fragment plates) |
| III | Comminuted, entire head, not reconstructable | Radial head arthroplasty |
| IV (Johnston) | Any fracture pattern + elbow dislocation | Treat as complex instability pattern |
Type I fractures are nondisplaced or minimally displaced (less than 2 mm). Type II fractures are displaced greater than 2 mm with partial head involvement and are amenable to ORIF. Type III fractures are comminuted with entire head involvement and are not reconstructable. Type IV (Johnston modification) adds an associated elbow dislocation to any radial head fracture pattern.
Management
Type I fractures are treated with sling or splint and early ROM; aspiration of hemarthrosis with local anesthetic injection may improve comfort and early motion. Type II fractures are treated with ORIF using headless compression screws and/or mini-fragment plates when there is a mechanical block to motion or greater than 2 mm displacement involving more than 30% of the articular surface. Type III fractures require radial head arthroplasty with a metallic prosthesis; it is critical to avoid overstuffing, with the prosthesis placed level with the proximal edge of the lesser sigmoid notch. Excision alone is only appropriate if the MCL is intact and there are no associated injuries, which is an increasingly rare indication. Type IV fractures are treated as part of the complex instability pattern.
<image>Mason classification of radial head fractures with treatment algorithm</image>
Coronoid Fractures
Classification
The Regan-Morrey classification divides coronoid fractures into Type I (tip avulsion), Type II (fragment less than 50% of the process), and Type III (greater than 50%). The O'Driscoll classification provides more anatomic precision with tip fractures (capsular avulsions), anteromedial facet fractures (associated with varus posteromedial rotatory instability), and basilar fractures (associated with transolecranon fracture-dislocations).
Anteromedial Facet Fractures
Anteromedial facet fractures represent a distinct injury pattern from the terrible triad. They are associated with varus posteromedial rotatory instability and require ORIF of the coronoid (buttress plate) plus LUCL repair. The approach is medial (over-the-top or FCU-splitting).
The Terrible Triad
Definition
The terrible triad comprises a posterior elbow dislocation combined with a radial head fracture and coronoid fracture. This combination was historically associated with poor outcomes due to recurrent instability and stiffness.
Pathomechanics
The mechanism involves axial load combined with valgus and supination (posterolateral rotatory mechanism). Three stabilizers are lost simultaneously: the coronoid (posterior buttress), the radial head (secondary valgus stabilizer), and the LUCL.
Systematic Surgical Approach (Inside-Out)
The systematic approach addresses structures in order from deep to superficial. First, the coronoid is repaired or fixed using a suture lasso technique for tip fractures or plate/screw fixation for larger fragments. Second, the radial head is treated with ORIF if reconstructable (Mason II) or arthroplasty if comminuted (Mason III). Third, the LUCL is repaired with suture anchors to the lateral epicondyle at the isometric point. Fourth, the MCL is repaired only if the elbow remains unstable after lateral-sided repair, assessed under fluoroscopy. Fifth, a hinged external fixator is applied if the elbow remains unstable after all repairs, serving as a last resort.
Postoperative Protocol
Active motion within the stable arc begins as early as possible. A hinged elbow brace is locked in the stable arc. Varus stress and forced extension are avoided. The goal is to maintain a concentric reduction throughout rehabilitation.
Olecranon Fractures
Classification
The Mayo classification grades olecranon fractures as Type I (undisplaced), Type II (displaced but stable, with subtypes A for noncomminuted and B for comminuted), and Type III (displaced and unstable, representing fracture-subluxation patterns).
Treatment
Nondisplaced fractures are splinted in 45-90 degrees of flexion with early ROM. Displaced fractures require surgical fixation. Tension band wiring is appropriate for simple, transverse fractures without comminution, converting distraction forces to compression. Plate fixation with precontoured plates is indicated for comminuted fractures, oblique fractures, Monteggia variants, and fracture-dislocations, offering biomechanical superiority. Excision with triceps advancement is reserved for elderly, low-demand patients with comminuted fractures, excising no more than 50% of the olecranon.
Monteggia Fracture-Dislocations
Bado Classification
The Bado classification describes four types: Type I involves anterior radial head dislocation with ulnar shaft fracture angulated anteriorly (most common in children); Type II involves posterior radial head dislocation with posterior ulnar angulation (most common in adults); Type III involves lateral radial head dislocation with proximal ulnar metaphyseal fracture; and Type IV involves anterior radial head dislocation with fractures of both the radius and ulna.
Treatment Principles
Anatomic reduction and rigid fixation of the ulna typically results in spontaneous reduction of the radial head. If the radial head does not reduce after ulnar fixation, the surgeon should look for an interposed annular ligament, entrapped capsule, or inadequate ulnar reduction. A post-fixation radiograph confirming radial head alignment with the capitellum on all views must always be obtained.
<image>Terrible triad injury pattern on lateral elbow radiograph showing posterior dislocation with coronoid and radial head fractures</image>
Elbow Stiffness
Prevention and Management
Intrinsic causes include articular incongruity, hardware, and heterotopic ossification. Extrinsic causes include capsular contracture, collateral ligament contracture, and heterotopic ossification. Prevention focuses on early motion and indomethacin or radiation for HO prophylaxis in high-risk patients. Surgical treatment involves open or arthroscopic capsular release (anterior and posterior), with careful attention to the ulnar nerve during posterior medial capsular release, which must always be identified and protected or transposed.
Clinical Pearls
The "drop sign" on lateral radiograph (widened ulnohumeral joint space) after reduction suggests persistent instability and must not be ignored. Forearm rotation should always be checked after radial head fixation or arthroplasty, as a block to rotation may indicate hardware prominence or prosthesis malpositioning. In terrible triad injuries, the coronoid is the most important structure to restore, and even tip fractures should be addressed surgically. Heterotopic ossification risk factors include head injury, burns, high-energy mechanism, and delayed surgery; prophylaxis with indomethacin 75 mg daily for 6 weeks is recommended. After radial head arthroplasty, the prosthesis should articulate at the level of the lateral crista of the trochlea, and positive ulnar variance should be checked to avoid overstuffing. CT scan is essential for preoperative planning of all complex elbow fracture-dislocations and should not be replaced by radiographs alone.
References
- O'Driscoll SW, Jupiter JB, King GJ, et al. The unstable elbow. Instr Course Lect. 2001;50:89-100.
- Mason ML. Some observations on fractures of the head of the radius with a review of one hundred cases. Br J Surg. 1954;42(172):123-132.
- Regan W, Morrey BF. Fractures of the coronoid process of the ulna. JBJS Am. 1989;71(9):1348-1354.
- Pugh DM, et al. The terrible triad of the elbow. J Hand Surg Am. 2004;29(1):85-95.
- Ring D, Jupiter JB. Fracture-dislocation of the elbow. JBJS Am. 2004;86(8):1759-1764.
- Bado JL. The Monteggia lesion. Clin Orthop Relat Res. 1967;50:71-86.
